When oxygen (O2) is electrolytically reduced, in the case of one-electron reduction, superoxide (.O2−) is generated, in the case of two-electron reduction, hydrogen peroxide is generated, and in the case of four-electron reduction, water is generated (Non-Patent Document 1).
In an electrochemical device wherein an oxygen reduction reaction is a positive-electrode reaction, in order to obtain a high capacity, high voltage, and high power, it is necessary to promote such reduction reaction at a noble (plus) potential while preventing overvoltage. In other words, it is preferable that a material that can promote a four-electron reduction reaction at a high potential while preventing occurrence of overvoltage be used as the catalyst component for the positive electrode (oxygen-reducing electrode). The following documents report such catalysts.
Patent Documents 1 and 2 disclose catalysts formed of a porous molded article formed of a fluoride resin and conductive powder carrying iron phthalocyanines, cobalt porphyrins and like metal chelate compounds having oxygen-reducing abilities. These documents also disclose that, when a dimer (binuclear complex) of a metal chelate compound is used, high oxygen-reducing ability (four-electron reduction ability) can be expected, and therefore a high-power air cell can be obtained.
Non-Patent Document 2 discloses oxygen-reducing catalysts using a macrocyclic complex (e.g., a cobalt porphyrin binuclear complex) containing Cr, Mn, Fe, Co and like transition metals as center metals.
Patent Document 3 discloses an oxygen-reducing manganese complex. This complex catalyzes a four-electron oxygen reduction reaction with high selectivity. Patent Document 3 also discloses that the manganese atom has a valency of 2 to 7 and catalyzes oxygen reduction reaction in the potential range of from −0.5 V to +2 V.
However, the metal complexes disclosed in these documents have the following drawback. These metal complexes oxidize and deteriorate constituent components of cells and/or sensors, such as electrolytes, electrode reeds, current collectors, cell cases, separators, gas selective transmission membranes, etc.
Patent Document 4 discloses an oxygen-reducing complex electrode as a technique for overcoming the above drawback. This oxygen-reducing complex electrode apparently achieves four-electron reduction reaction with selectivity of almost 100%, despite this oxygen-reducing complex electrode not containing a highly oxidative catalytic component such as a metal complex containing a high valency center metal, etc.
Specifically, this oxygen-reducing complex electrode comprises Catalyst A which catalyzes a two-electron oxygen reduction reaction and Catalyst B which decomposes hydrogen peroxide formed by the two-electron oxygen reduction reaction into oxygen and water.
Metal phthalocyanines such as iron phthalocyanines, cobalt phthalocyanines, copper phthalocyanines, manganese phthalocyanines, and zinc phthalocyanines can be used as Catalyst A. Patent Document 4 discloses the following four cobalt phthalocyanine compounds.                Cobalt 4,4′,4″,4′″-tetraaminophthalocyanine (abbreviated as COTAPc) represented by Structural Formula (a) below and polymers thereof;        Cobalt hexadecafluorophthalocyanine (abbreviated as CoHFPc) represented by Structural Formula (b) below;        Cobalt tetracarboxyphthalocyanine (abbreviated as CoCOOHPc) represented by Structural Formula (c) below; and        Cobalt octabutoxyphthalocyanine (abbreviated as CoOBuPc) represented by Structural Formula (d) below.        
Non-Patent Document 3 discloses cobalt octacyanophthalocyanine (abbreviated as CoPc(CN)8) represented by Structural Formula (e) below as a cobalt phthalocyanine compound that functions the same as Catalyst A does.
Patent Document 5, and Non-Patent Document 4 also relate to the present invention.

[Patent Document 1] Japanese Examined Patent Publication No. 1990-030141
[Patent Document 2] Japanese Examined Patent Publication No. 1990-030142
[Patent Document 3] Japanese Unexamined Patent Publication No. 1999-253811
[Patent Document 4] Japanese Unexamined Patent Publication No. 2003-151567
[Patent Document 5] Japanese Unexamined Patent Publication No. 1999-65142
[Non-Patent Document 1] Edited by Jacek Kipkowski and Philip N. Ross, Electrocatalysis, Wiley-Vch, (1998): 204-205
[Non-Patent Document 2] Edited by Jacek Kipkowski and Philip N. Ross, Electrocatalysis, Wiley-Vch, (1998): 232-234
[Non-Patent Document 3] Journal of Electrochemical Society, Vol. 15, 2004: A2047-A2052
[Non-Patent Document 4] Tetrahedron Letters, Vol. 41, 2000: 9267-9270